As disclosed in, for example, a patent document 1, a current sensor has been proposed that includes a bus bar, a magnetic detector positioned relative to the bas bar so that a magnetic field induced by a current flowing through the bus bar can be applied to a magnetic responsive surface, and a magnetic shield which magnetically shields the magnetic detector. The magnetic shield has a ring-shaped surrounding portion to surround the bus bar and the magnetic detector inside, and the ring-shaped surrounding portion has a gap, at least, at one position. When a height direction is defined as a direction of a line passing the bus bar and the magnetic detector on an imaginary plane which is perpendicular to a length direction of the bus bar and contains a position where the magnetic detector exists, the gap and the bus bar are located at the same or almost the same position in the height direction.
The bus bar has a plate shape having a thickness direction along the height direction. A magnetic responsive direction of the magnetic responsive surface is the same as a width direction of the bus bar. Therefore, the magnetic detector does not respond to a magnetic field in the height direction.
As described above, in the current sensor disclosed in the patent document 1, the gap and the bus bar are located at the same or almost the same position in the height direction. A magnetic flux flowing in the magnetic shield is discharged through the gap and generates a magnetic field outside. The magnetic field generated by the gap (hereinafter referred to as a gap magnetic field) varies depending on a shape of the magnetic shield. In the case of a structure shown in FIG. 1, since the shape of the magnetic shield is symmetrical with respect to a line connecting two gaps (hereinafter referred to as a reference line), the gap magnetic field is orthogonal to the reference line. In the patent document 1, although the gap and the bus bar are located at the same or almost the same position in the height direction, the gap and the magnetic detector are not located at the same position in the height direction. Therefore, the gap magnetic field is applied obliquely to the magnetic detector, and the gap magnetic field along the width direction of the bus bar is applied to the magnetic responsive surface. As a result, a resistance of a magnetoresistive effect element may change, so that accuracy of detecting current may be reduced.